In use, gas sensor devices which measure the concentration of a given gas component such as nitrogen oxide (NOx) are arranged in an exhaust pipe of an internal combustion engine. In the gas sensor devices, voltage is applied between a pair of electrodes disposed on a front and a back surface of a solid electrolyte body to regulate the concentration of oxygen in the exhaust gas, i.e., a measurement gas to be less than or equal to a given concentration. In order to enhance the accuracy in determining the concentration of the given gas component, the concentration of oxygen which still remains after the concentration of oxygen is regulated is measured or further regulated.
For instance, Japanese Patent First Publication No. 2002-310987 discloses a gas sensor device which regulates the concentration of oxygen in the measurement gas using an oxygen pump cell made by a pair of electrodes disposed on a solid electrolyte body and measures the concentration of oxygen remaining in the measurement gas using an oxygen monitor cell made of a pair of electrodes disposed on the solid electrolyte body. The gas sensor device works to measure the concentration of the given gas component in the measurement gas using a sensor cell made of a pair of electrodes disposed on the solid electrolyte body. An ion current value representing the concentration of residual oxygen is subtracted from an oxygen ion current value, as derived as indicating the concentration of the given gas component to reduce effects of the residual oxygen on determination of the concentration of the given gas component.